LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITED SILICON-RICH OXIDES FOR NONVOLATILE MEMORY APPLICATIONS

The electrical and reliability characteristics of ultrathin nonstoichiometric silicon oxide (SiOx, x < 2) films deposited by the low-pressure chemical vapor deposition (LPCVD) technique using silane and nitrous oxide were studied. It has been found that these oxides exhibit enhanced current conduction at low electric field for both voltage polarities due to reduced conduction barrier height and a conduction mechanism that involves direct tunneling between dispersed silicon crystallites in the oxide. The current characteristics are controlled by adjusting the SiH4 / N2O gas ratio. These nonstoichiometric films exhibit lower charge trapping, have an extremely large charge to breakdown, and there is negligible interface state generation in comparison to ultrathin thermal oxides. The results indicate that these highly reliable ultrathin dielectrics can be promising candidates for nonvolatile memory applications.